22221: Near Repdigit 22..221

First few terms (base 10): \[[2^*1_7]_n=\{1,15,113,799,5601,\ldots\}\]

First few terms (base 7): \[\{\text{1},\text{21},\text{221},\text{2221},\text{22221},\ldots\}\]

General Formula:\[[2^*1_7]_n={7\cdot7^{n}-4\over3}\]

Equivalent Patterns: \[[6^*3_7]_n=3\cdot[2^*1_7]_n\] \[[4^*2_7]_n=2\cdot[2^*1_7]_n\]

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